The present invention relates to a process for forming microcapsules wherein the microcapsule wall is formed from an amine-formaldehyde resin. More particularly, it relates to a process for forming urea-formaldehyde microcapsules wherein the urea-formaldehyde resin is condensed in the presence of a polyol.
U.S. Pat. Nos. 4,089,802 and 4,001,140 describe a process for producing urea-formaldehyde microcapsules wherein the capsule wall is formed in the presence of a negatively charged polyelectrolyte. That polyelectrolyte is a carboxyl-substituted, linear aliphatic material. The function of the polyelectrolyte is that of a system modifier. The polyelectrolyte reportedly controls the formation of the condensation polymer such that the encapsulation process can be carried out without continually diluting the encapsulation medium as reportedly is required with earlier processes. The function of the modifier is reflected in a reduction in the viscosity of the system at higher polymer concentrations.
The system modifiers disclosed in U.S. Pat. Nos. 4,089,802 and 4,001,140 are maleic anhydride copolymers. Representative examples are isobutylene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, propylenemaleic anhydride copolymer, and butadiene-maleic anhydride copolymer. The molecular weight of these materials must exceed a certain minimum molecular weight to avoid gelling or thickening of the encapsulation medium.